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Results for “model predictive control”

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PubMed2006

Dexterity in cerebellar agenesis.

Given the well established role of the cerebellum in motor control, deficient motor performance during life time appears to be common in cerebellar agenesis. However, behavioural data on motor performance in living subjects with cerebellar agenesis are scarce. Dexterity during object manipulation was comparatively investigated in a 63-year old female with cerebellar agenesis and three healthy age- and gender-matched control subjects. Participants performed a transport task with an instrumented object and caught a weight that was dropped into a hand-held receptacle either expectedly from the opposite hand or unexpectedly from the experimenter's hand. Compared to healthy subjects, the subject with cerebellar agenesis generated greater grasping forces. For the transport task the patient showed a clear impairment of the predictive adjustment of grasping forces to the differential loading requirements of movement direction. For the weight-catching task, the patient established an accurate reactive mode of control when the weight was dropped unexpectedly. In case the weight was dropped expectedly from the opposite hand, predictive control mechanisms were severely disturbed in the subject with cerebellar agenesis. These data highlight the role of the cerebellum for predictive force control and are interpreted within the concept of internal models reflecting the causal relationship between actions and their consequences.

Aged↗

PubMed2004

Sexual functioning and quality of life after prostate cancer treatment: considering sexual desire.

OBJECTIVES: To evaluate whether the relationship between sexual desire and quality of life (QOL) is moderated by sexual functioning in 91 men who had received treatment for localized prostate cancer within the past 18 months. METHODS: Items from the University of California, Los Angeles, Prostate Cancer Index and Expanded Prostate Cancer Index Composite were used to assess sexual factors, and the Functional Assessment of Cancer Therapy--General Module was administered to evaluate QOL. Education, income, and the Charlson comorbidity index were significantly related to QOL and controlled in all analyses. We tested a moderated regression model to predict QOL. RESULTS: Although a main effect was detected for sexual functioning, the interaction of sexual desire and sexual functioning added a significant amount to the explained variance in QOL. Post hoc tests of moderation revealed that men with lower sexual functioning had significantly lower QOL scores as the level of sexual desire increased, suggesting that desire in the absence of adequate functioning may result in poorer QOL. Additionally, a tendency was found for men with better sexual functioning to have higher QOL scores as the level of sexual desire increased. CONCLUSIONS: The results of our study suggest that both sexual desire and sexual functioning are necessary for optimal QOL and highlight the utility of considering these two facets of sexuality independently to maximize the prediction of variance in QOL scores.

Aged↗

PubMed2002

Grey-box modelling of aeration tank settling.

A model of the concentrations of suspended solids (SS) in the aeration tanks and in the effluent from these during Aeration tank settling (ATS) operation is established. The model is based on simple SS mass balances, a model of the sludge settling and a simple model of how the SS concentration in the effluent from the aeration tanks depends on the actual concentrations in the tanks and the sludge blanket depth. The model is formulated in continuous time by means of stochastic differential equations with discrete-time observations. The parameters of the model are estimated using a maximum likelihood method from data from an alternating BioDenipho waste water treatment plant (WWTP). The model is an important tool for analyzing ATS operation and for selecting the appropriate control actions during ATS, as the model can be used to predict the SS amounts in the aeration tanks as well as in the effluent from the aeration tanks.

Air↗

PubMed2000

Paternal investment and the human mating system.

Paternal investment has long been considered responsible for the evolution of predominantly monogamous marriage in humans. However, male-male competition resulting in mate-guarding and male coercion could be equally important. In this review, I use a comparative approach to examine the effect of variation in human paternal investment on our mating system. I conclude paternal investment is important but so too is mate-guarding. I propose a model of our mating system incorporating both factors. Variation in the mating system is explained by variation in male resource control and contribution, resulting in ecologically imposed monogamy or polygyny, as predicted by the polygyny threshold model, as well as variation in male-male competition for status, resulting in socially imposed monogamy or polygyny.

Journal Article↗

PubMed2026

Patient-specific modeling identifies metabolic interventions for reversing glucose use reprogramming in alcohol-associated hepatitis.

Alcoholic hepatitis (AH) is an acute form of alcohol-associated liver disease with very few treatment options. Recent studies highlighted liver metabolic reprogramming in AH as an indicator of severity. We aim at identifying new intervention points to reverse liver metabolic dysregulation across varying degrees of AH. We develop 89 personalized genome-scale metabolic models by integrating a generic human cellular metabolic model with liver transcriptomics data from AH patients with varying disease severity and healthy controls. We grade the AH patients based on the model-predicted level of glycolysis reprogramming and validate the results using published metabolomics data. We test in silico gene knockdown interventions to reverse the aberrant metabolic reprogramming in AH. Knockdown of two glycolytic genes, Hkdc1 and Pkm, significantly rebalance the metabolic fluxes toward a healthy liver metabolic phenotype. We use machine learning on the glycolysis fluxes to develop a quantitative glucose use reprogramming score, which correlates with AH severity and patient-specific responses to in silico gene knockdown interventions. The score was independently validated using a published AH liver transcriptomics dataset. We propose a cellular metabolism-based therapy targeting Hkdc1 and Pkm in the glycolysis pathway as a potential treatment for reversing the aberrant glucose metabolism in AH.

Humans↗

PubMed2004

Fatigue during pregnancy predicts caesarean deliveries.

BACKGROUND: Previous studies on fatigue and pregnancy outcomes were confined to women with occupational fatigue and did not include women who did not work outside the home. Fatigue during mid- and late pregnancy has rarely been studied. AIMS: This paper reports a study examining the associations between work factors, household factors, and fatigue among low-risk pregnant women in Taiwan and links the effects of fatigue to preterm births and caesarean deliveries. METHODS: The participants were 633 women who were 20-36 weeks pregnant without evidence of obstetrical complications at the time of interview. Pregnancy outcomes were abstracted from the hospital records after delivery. Fatigue was measured using the Fatigue Symptom Checklist. Women were categorized into three groups according to their work status: non-working, sedentary work, and active work. Other work factors included hours worked and exposure to adverse work environments. Household factors included household work and childcare responsibilities. Multiple linear regression and logistic regression were used for the analysis. RESULTS: The factors significantly associated with fatigue in the regression model were age, infection during pregnancy, bleeding after 12 weeks of pregnancy, and work status. Women who did not work outside of the home had significantly higher fatigue scores than those who did sedentary work outside the home. Younger women had higher fatigue scores than older women. Fatigue scores during pregnancy predicted caesarean deliveries, given that age and obstetrical risks were controlled in the model. CONCLUSIONS: Fatigue is a significant problem for pregnant women. Fatigue assessments should include morbidities during pregnancy as well as household and work-related factors. Special attention should be paid to women who do not work outside the home. Staff should elicit information about fatigue and intervene early, as this may help decrease the number of caesarean deliveries.

Activities of Daily Living↗

PubMed1998

Dispersion pre-compensation of 15 femtosecond optical pulses for high-numerical-aperture objectives.

The excitation efficiency in two-photon absorption (TPA) microscopy depends strongly - owing to the square dependence of the TPA fluorescence on the excitation intensity - on the temporal width of the excitation pulse. Because of their inherently large frequency bandwidth, ultrashort optical pulses tend to broaden substantially because of dispersion from propagation through the dispersive elements in the microscope. In this paper, the dispersion characteristics of a wide range of microscope objectives are investigated. It is shown that the induced dispersion can be pre-compensated in all cases for pulses as short as 15 fs. Because of the excellent agreement between the results from theoretical modelling and the experimental data, predictions of the possibility of dispersion control for microscope objectives in general, as well as for even shorter pulses, can be inferred. Since for TPA imaging the background due to single photon absorption processes and scattering is independent of the pulse width, proper dispersion pre-compensation - which minimizes the pulse duration at the focal point and hence maximizes the excitation efficiency - provides optimal image contrast in TPA microscopy.

Journal Article↗

PubMed2001

Secondary structure of the human cardiac Na+ channel C terminus: evidence for a role of helical structures in modulation of channel inactivation.

Little is known about the structure of the C terminus of the human cardiac voltage-gated sodium channel alpha subunit (SCN5A), but disease-linked mutations within this 244-amino acid intracellular region of the channel have marked effects on channel inactivation. Here we report a structural analysis of the C-terminal tail of the cardiac Na(+) channel that sheds new light on mechanisms that control its inactivation gating. Homology modeling of the SCN5A C terminus predicts predominant alpha-helical structure (six helices) in the proximal half of this intracellular tail but little structure in the distal half. Circular dichroism of isolated and purified C terminus supports this prediction. Whole cell and single channel patch clamp recordings of wild type and mutant alpha subunits co-expressed with the hbeta(1) subunit in HEK 293 cells indicate that truncation of the distal, nonstructured, C terminus (L1921stop mutant) reduces current density but does not affect channel gating (n = 6). In contrast, truncation of the sixth helix containing a concentration of positively charged residues along with the distal C terminus (S1885stop mutant) also reduces current density but, in addition, has profound and selective effects on inactivation (no effect on activation). Channel availability is shifted (-11 +/- 0.6 mV), and there is a 10-fold increase in the percentage of channels that burst (fail to inactivate) during prolonged depolarization (0.025% S1885stop (n = 7) versus 0.0028% wild type (n = 9), p < 0.005). These results suggest that the charged structured region of the SCN5A C terminus plays a major role in channel inactivation, stabilizing the inactivated state.

Amino Acid Sequence↗

PubMed2000

A model for pulse jet fabric filters.

A new model for pulse jet fabric filtration is proposed. In contrast to the earlier model of Ravin and Humphries, which was formulated on the steady state assumption, the present study is aimed at developing a predictive capability for both transient and steady state operations, taking into account the compression effect of filter cakes. The model's relative simplicity allows frequent updating of the model parameter values, thus improving the accuracy of predictions. As a result, the model is particularly useful in developing control algorithms and designing controllers of pulse jet fabric filtration systems.

Air Pollution↗

PubMed2003

Predicting attrition in a pediatric asthma intervention study.

OBJECTIVES: To operationalize a comprehensive description of attrition, including pre-inclusion, dropout, and attrition due to intermittent missing data, and to test a predictive model of attrition using a data set from a randomized controlled intervention in pediatric asthma. METHODS: Participants included children, ages 4-12, diagnosed with asthma and their caregivers. Demographic variables and outcome measures of asthma morbidity were examined in 327 families to determine their association with attrition. RESULTS: Families who did not complete randomization and the intervention tended to have younger caregivers than did completers. Caregiver age emerged as the most consistent predictor of pre-inclusion and dropout attrition. There were no significant predictors of attrition due to intermittent missing data. CONCLUSION: Younger caregivers may be at particular risk for attrition in pediatric asthma intervention studies and warrant special attention by investigators.

Asthma↗

PubMedDate not supplied

The relationship of somatization and depression to experimental pain response in women with temporomandibular disorders.

OBJECTIVE: Patients with temporomandibular pain disorders (TMD) have greater experimental pain perception when compared with pain-free controls. Common psychological features of TMD include somatization and depression. The impact of depression on experimental pain perception has received considerable attention. However, the role of somatization on experimental pain in a chronic pain population has not been explored. METHODS: Fifty-six women with TMD and 59 pain-free controls underwent three experimental pain procedures, including palpation at fixed amounts of pressure, pressure pain thresholds, and an ischemic pain task. Levels of depression and somatization were assessed using the Research Diagnostic Criteria for TMD. Multiple regression analyses were performed to determine the extent to which depression and somatization were associated with experimental pain response. RESULTS: After controlling for characteristic pain intensity and depression, somatization explained a significant proportion of variance in numbers of masticatory sites rated as painful (R2 change = 6.7%, p = .046) with the full model explaining 16.4% of the variance (p = .024). This did not meet an adjusted level of statistical significance (p = .008). After controlling for characteristic pain, only depression added significantly to the model predicting ischemic pain threshold and tolerance. The full models including characteristic pain and depression explained 49% and 20% of the variance in ischemic pain threshold and tolerance, respectively. CONCLUSIONS: These findings suggest that depression and somatization are associated with different measures of experimental pain. Somatization may be related to more attentional and perceptual measures of clinically relevant pain while depression may be related to more behavioral measures of pain.

Adolescent↗

PubMed1995

A minimal model for T-cell vaccination.

We have developed a mathematical model for the regulation of the growth of autoreactive T cells (the T cells responsible for autoimmunity). The model is very simple in that it is based only on the fundamental properties of T cells. However, despite this simplicity, it can account for a variety of phenomena referred to as T-cell vaccination. The purpose of T-cell vaccination is to create resistance to autoimmunity. This can be achieved by injecting either a subpathogenic quantity of autoreactive T cells, or attenuated autoreactive cells, or cells that recognize the autoreactive cells. The results of our model are based on the assumption that the self antigens involved in T-cell vaccination are normally not expressed; thus the autoreactive T lymphocytes are neither activated nor negatively selected. Self tolerance, therefore, corresponds to a 'passive' state. T-cell vaccination induces a transition from this passive state of tolerance to an active state of tolerance. In this state the autoreactive cells are controlled by regulator cells which recognize the autoreactive cells. The model predicts a qualitative difference between vaccination with normal autoreactive cells and vaccination with attenuated autoreactive cells. Normal cells may give rise to a permanent switch to the vaccinated state; attenuated cells, however, can provide only transient protection, which is dose dependent. Preliminary experimental data confirm this prediction. Finally, we propose a speculative explanation for relapsing autoimmune disease.

Animals↗

PubMed2005

Fault tolerant control of multivariable processes using auto-tuning PID controller.

Fault tolerant control of dynamic processes is investigated in this paper using an auto-tuning PID controller. A fault tolerant control scheme is proposed composing an auto-tuning PID controller based on an adaptive neural network model. The model is trained online using the extended Kalman filter (EKF) algorithm to learn system post-fault dynamics. Based on this model, the PID controller adjusts its parameters to compensate the effects of the faults, so that the control performance is recovered from degradation. The auto-tuning algorithm for the PID controller is derived with the Lyapunov method and therefore, the model predicted tracking error is guaranteed to converge asymptotically. The method is applied to a simulated two-input two-output continuous stirred tank reactor (CSTR) with various faults, which demonstrate the applicability of the developed scheme to industrial processes.

Algorithms↗

PubMed2005

Human postural sway results from frequent, ballistic bias impulses by soleus and gastrocnemius.

It has been widely assumed for nearly a century, that postural muscles operate in a spring-like manner and that muscle length signals joint angle (the mechano-reflex mechanism). Here we employ automated analysis of ultrasound images to resolve calf muscle (soleus and gastrocnemius) length changes as small as 10 mum in standing subjects. Previously, we have used balancing of a real inverted pendulum to make predictions about human standing. Here we test and confirm these predictions on 10 subjects standing quietly. We show that on average the calf muscles are actively adjusted 2.6 times per second and 2.8 times per unidirectional sway of the body centre of mass (CoM). These alternating, small (30-300 microm) movements provide impulsive, ballistic regulation of CoM movement. The timing and pattern of these adjustments are consistent with multisensory integration of all information regarding motion of the CoM, pattern recognition, prediction and planning using internal models and are not consistent with control solely by local reflexes. Because the system is unstable, errors in stabilization provide a perturbation which grows into a sway which has to be reacted to and corrected. Sagittal sway results from this impulsive control of calf muscle activity rather than internal sources (e.g. the heart, breathing). This process is quite unlike the mechano-reflex paradigm. We suggest that standing is a skilled, trial and error activity that improves with experience and is automated (possibly by the cerebellum). These results complement and extend our recent demonstration that paradoxical muscle movements are the norm in human standing.

Adult↗

PubMed2006

Vivo motion and force measurement of surgical needle intervention during prostate brachytherapy.

In this paper, we present needle insertion forces and motion trajectories measured during actual brachytherapy needle insertion while implanting radioactive seeds in the prostate glands of 20 different patients. The needle motion was captured using ultrasound images and a 6 degree-of-freedom electromagnetic-based position sensor. Needle velocity was computed from the position information and the corresponding time stamps. From in vivo data we found the maximum needle insertion forces to be about 15.6 and 8.9 N for 17 gauge (1.47 mm) and 18 gauge (1.27 mm) needles, respectively. Part of this difference in insertion forces is due to the needle size difference (17G and 18G) and the other part is due to the difference in tissue properties that are specific to the individual patient. Some transverse forces were observed, which are attributed to several factors such as tissue heterogeneity, organ movement, human factors in surgery, and the interaction between the template and the needle. However, theses insertion forces are significantly responsible for needle deviation from the desired trajectory and target movement. Therefore, a proper selection of needle and modulated velocity (translational and rotational) may reduce the tissue deformation and target movement by reducing insertion forces and thereby improve the seed delivery accuracy. The knowledge gleaned from this study promises to be useful for not only designing mechanical/robotic systems but also developing a predictive deformation model of the prostate and real-time adaptive controlling of the needle.

Brachytherapy↗

PubMed2001

Egalitarianism in female African lions.

Because most cooperative societies are despotic, it has been difficult to test models of egalitarianism. Female African lions demonstrate a unique form of plural breeding in which companions consistently produce similar numbers of surviving offspring. Consistent with theoretical predictions from models of reproductive skew, female lions are unable to control each other's reproduction because of high costs of fighting and low access to each other's newborn cubs. A female also lacks incentives to reduce her companions' reproduction, because her own survival and reproduction depend on group territoriality and synchronous breeding. Consequently, female relationships are highly symmetrical, and female lions are "free agents" who only contribute to communal care when they have cubs of their own.

Animals↗

PubMed1994

A mathematical model of intraluminal and intracavitary brachytherapy.

The adaptation of the linear-quadratic model to allow for the effect of tumour regression and clonogen repopulation between initial teletherapy and subsequent brachytherapy has been extended to include the geometrical conditions encountered in intraluminal and intracavitary brachytherapy. For a radiation line source placed at the centre of a lumen or cavity, regression of any endoluminal tumour towards its mural origin will not result in any change in the minimum brachytherapy-tumour dose with time. In contrast, regression of transmural tumour will cause a potentially advantageous increase in the minimum brachytherapy-tumour dose with time. The latter effect will be opposed by tumour clonogen repopulation. The log(e) cell kill due to brachytherapy has been calculated for tumours of diameters 2, 4 and 6 cm at completion of teletherapy. The centres of the tumours were assumed to be at distances of 0, 1 and 2 cm from the radiation source. Tumour linear regression rates (lambda) ranging from 0.025 to 0.25 per week and tumour clonogen doubling times (Tp) of 2.5, 5 and 15 days were used in the calculations. The results demonstrate the critical importance of the distance of the tumour centre from the line source as well as the influence of tumour diameter, lambda and Tp. In some instances, both maximum and minimum values of log(e) cell kill occur. Calculations of tumour cure probabilities reveal that these variations in log(e) cell kill predicted by the model can produce highly significant differences in tumour control rates. Where the relevant parameters can be assessed directly or estimated from previous experience, the model provides a basis for the design of future intraluminal or intracavitary brachytherapy protocols.

Brachytherapy↗

PubMed2002

Misalignment tolerance analysis of free-space optical interconnects via statistical methods.

System-level packaging is one of the critical issues that need to be addressed for free space optical interconnections (FSOI) to become useful in desktop systems. The performance of FSOI, e.g., in terms of system bit-error rate, is greatly affected by misalignments in the optical system. Therefore tolerancing, i.e., the ability to analyze and predict the effects of misalignments in the system, is of prime importance to system designers. We introduce an approach in which we study the effects of optical misalignments and other tolerance factors using statistical methods. We use Monte Carlo simulations, design of the experiments, and regression techniques to fit a polynomial equation that expresses the relationship between the system performance and the tolerance factors. This prediction model can be used for design, cost optimization, and quality control purposes. In addition, we perform a sensitivity analysis to determine those tolerance variables that have the greatest effect on system performance.

Journal Article↗